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Publication: Caesarean sections and low birth weight in Kenya related to higher heat stress

A new HIGH Horizons study published in the Journal of Climate and Health this month has found that higher heat stress leads to a raised likelihood of caesarean sections and babies born with low birth weight in Kenya.

The study was the first of its kind for Kenya, and the first time the relationship between heat stress and caesarean sections was analysed in a low-income setting.

The study’s key findings:

  • High heat exposure on the day of birth led to an increased likelihood of caesarean sections. (i.e. the relative risk ratio at the 95th percentile in comparison to the median exposure was 1.21 (1.01,1.46) 95 % CI for maximum UTCI).
  • High heat exposure 1 and 2 months before birth led to an increased likelihood of low birth weight.
  • We present a tipping point for the increased likelihood of caesarean sections in Kenya of 26°C mean UTCI, which is originally the moderate heat stress threshold in this index. And suggest other studies consider such thresholds, which we acknowledge do change across climate zones and with acclimatization, type of work and clothing.


Researchers analysed the relationships between a variety of measures of heat stress, including wet bulb globe temperature (WBGT), the Universal Thermal Climate Index (UTCI), and temperature, with maternal and neonatal outcomes, including: low Apgar score (score below 7 at 5 min), stillbirth (death of the baby after 28 weeks prior to delivery), preterm birth (birth before 37 weeks), long duration of stay in hospital (>5 days in hospital), assisted vaginal deliveries, low birth weight (baby weighs <2500 g) and caesarean sections.

The study also used a novel method measuring heat stress monthly to analyse the relationship to birth outcomes on a month-by-month timescale.

Chloe Brimicombe, a climate scientist at the London School of Hygiene and Tropical Medicine and lead author on the study, wants the study to inspire future research using similar methods. “My hopes are that it motivates people to look at the impacts of heat even if they don’t have the finest resolution data in countries, because there’s lots of data available on a monthly timescale,” she said.

She also hopes it serves as motivation for researchers and countries to increase their commitment to studying the problem. “They need to put more resources into the researching the impact of heat on maternal health and work with their country researchers to explore interventions,” she said.